Negative frequency dependent selection maintains shell banding polymorphisms in two marine snails (Littorina fabalis and L. saxatilis)

Daniel Estévez-Barcia, Juan Galindo & Emilio Rolán-Alvarez
The presence of shell bands is common in gastropods. The marine snails, Littorina fabalis and L. saxatilis, are both polymorphic for this trait. Such polymorphism would be expected to be lost by the action of genetic drift or directional selection, but it appears to be widespread at relatively constant frequencies. This suggests it is maintained by balancing selection on the trait or on a genetically linked trait. Using long time-series of empirical data, we compared...
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